1. Field of the Invention
This invention relates to a socket for an electric part, in which contacts are shifted to a contact release position by sliding a slider rearwardly, so that an electric part such as an IC can be inserted and removed under a no-load condition.
2. Prior Art
U.S. Pat. No. 4,623,208 discloses a socket of the same type as the present invention, including a plurality of contacts implanted in a base, the contacts each having a curved spring portion, a contact nose portion extending forwardly from an upper end of the curved spring portion, and a cantilevered arm integrally extending rearwardly from an upper end of the curved spring portion. The curved spring portion is compressed by pushing down an end portion of the cantilevered arm so that the contact nose portion is separated away from a corresponding lead of an electric part.
Specifically, when the cantilevered arm is pushed down in the above socket, a push-down force is applied to the upper end of the curved spring portion. Since the upper end of the curved spring portion is flexed downwardly against the elasticity thereof by the push-down forced, the contact nose portion is shifted rearwardly so as to be separated away from the corresponding lead in order to facilitate smooth insertion and removal of an IC.
In the above-mentioned prior art, if a spring constant of the curved spring portion is arranged to be large in order to increase a contacting pressure, the push-down force becomes correspondingly large. In contrast, if the spring constant of the curved spring portion is arranged to be small in order to reduce an operating force, the contacting pressure is also lowered. Thus, the prior art alternatives have mutually incompatible problems as discussed. Accordingly, it is conventionally difficult to provide a design for which both the necessary operating force is arranged to be as small and the contacting pressure is large.
Furthermore, in a construction wherein the contact nose portion is shifted rearwardly by compressing the curved spring portion by pushing down the cantilevered arm, the problem occurs that it is difficult to obtain an efficient shifting amount relative to a pushing-down amount.
It further has the problem that when the cantilevered arm is pushed down, a twist tends to occur to the axis of the contact. As a result, a harmful swaying is likely to occur to the contact nose portion, and repeated application of an external force to the cantilevered arm in the curved direction easily accumulates metal fatigue to a basal portion of the cantilevered arm.